Coil ends of the plug wires are secure. Too soon to tell if it helped...only drove it about 10 miles today....but for those 10 miles it was rattless bliss...

 

Keep us posted....the multiple misfire thing...I'm perplexed after new wires/plugs. We'll see though...

 

Went to work last evening and it rattled all the way there and back. The trip is about 7 miles each way.

Just to refresh, it started out as a ping like sound. Very similar to if you use the wrong grade of fuel. It has since turned into a metalic rattle. I have been using either Sunoco 93 or Exxon 93 fuel and Lucal fuel addative.

It does not make the noise at idle either in gear or in neutral, only when driving.

New plugs & wires
1/3rd can of seafoam through the brake booster line "cured" it for a few days
Cats sound solid when I hit them
Y-pipe bolts are tight
Latest codes as of 5/8/10 were:
1194
1191
300
304
1316

 

You mentioned injectors earlier. Did you check them (especially cylinder#4)? First grab a tube from a paper towel and use it to listen for the clicking of each injector. Note if any are not clicking, or clicking irregularly. Then pull them one at a time and turn the key to acc and see if fuel sprays out. If it does, then that injector is stuck open.

Other than that, I'm drawing a blank on your symptoms...